BIZOMAT MAKEOS · Fasteners
Bolt and Pin Shear and Bearing
Are these bolts or pins strong enough in shear and bearing for this load?
Shear stress in bolts, dowels or clevis pins in single or double shear and the bearing stress on the plate, compared with allowable values.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Total load | N | Total shear load on the group (equal sharing assumed). |
| Number of bolts or pins | fasteners | Number of fasteners sharing the load. |
| Shear planes per fastener | choice | Single shear for a lap joint; double shear for a clevis or pin between two plates. |
| Diameter at the shear plane | mm | Diameter where the shear plane cuts: the shank diameter, or the thread minor diameter if threads are in the shear plane. |
| Thinnest plate thickness in bearing | mm | Thickness of the thinnest plate (or the sum of the two outer plates in double shear, whichever is smaller). |
| Allowable shear stress | MPa | Allowable shear stress of the fastener material from your design code. |
| Allowable bearing stress | MPa | Allowable bearing stress on the plate from your design code. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Total load
- What it is
- The whole shear load carried by the fastener group, which the tool shares equally between the fasteners.
- Units and format
- Enter a number in N: newtons. The form accepts 0.000001 N or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20000 N as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Shear and bearing stresses rise in proportion.
- Get it right
- Enter the total load on the group, not the load per bolt. Eccentric loads do not share equally.
What this means: Number of bolts or pins
- What it is
- How many bolts or pins share the load equally in the joint.
- Units and format
- Enter a number in fasteners: fasteners. The form accepts 1 fasteners to 1000 fasteners. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 fasteners as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Both stresses fall in proportion to the number of fasteners.
- Get it right
- Count only fasteners that actually carry the load in shear.
What this means: Shear planes per fastener
- What it is
- How many times each fastener is cut by a shear plane: once in a lap joint, twice in a clevis or a pin between two outer plates.
- Units and format
- Choose one of 2 options from the list: Single shear; Double shear.
- Example
- The form opens with “Single shear” selected as a worked example. Choose the option that matches your case.
- Get it right
- Double shear halves the shear stress but does not change the bearing stress the tool calculates.
What this means: Diameter at the shear plane
- What it is
- The fastener diameter where the shear plane passes: the plain shank, or the thread minor diameter if the thread lies in the shear plane.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Shear stress falls with the square of diameter; bearing stress falls in proportion.
- Get it right
- Use the minor diameter when threads cross the shear plane; the nominal size overstates the shear area.
What this means: Thinnest plate thickness in bearing
- What it is
- The plate thickness that the fastener bears against: the thinnest plate, or in double shear the smaller of the middle plate and the two outer plates together.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 8 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Bearing stress falls in proportion to thickness.
- Get it right
- Take the governing thickness, not the total stack.
What this means: Allowable shear stress
- What it is
- The shear stress the fastener material may carry in your design, from your design code or standard for that material and grade.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 100000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 150 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use an allowable value that already includes your code’s safety margin, not the ultimate shear strength.
What this means: Allowable bearing stress
- What it is
- The bearing (crushing) stress the plate material may carry around the hole, from your design code.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 100000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 250 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the value for the plate, not the fastener, unless the fastener is the softer material.
Method and formulas
- Shear τ = F ÷ (n × planes × πd²/4).
- Bearing σ_b = F ÷ (n d t).
- Utilisation = stress ÷ allowable; the larger governs.
- Example: 20000 N on 2 × 10 mm bolts in single shear gives τ = 127.32 MPa and bearing 125 MPa.
Limitations
- Equal load sharing; eccentric groups and slip-critical (friction) joints need other methods.
- Edge distance, net-section tension and block shear of the plates are not checked.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check clevis pins, hinge pins and dowels
- Check bolted lap and splice joints in shear
- Choose pin size and plate thickness
Who it is for
- Design engineers
- Maintenance fitters
- Quality inspectors
What you get
- Shear stress and its ratio to allowable
- Bearing stress and its ratio to allowable
- Governing mode
Interpreting the result
- Keep threads out of the shear plane, or use the minor diameter.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1535, 1720–1735. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
Joints in shear: bearing type and friction grip
In Bolted Joints by the Numbers
What it covers: How bolted joints carry shear: by bolts bearing on their holes or by the friction their preload creates, how to check each, and what painted faying surfaces do to slip.
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